Can you put a moister barrier on the floor joists instead of the dirt floor the dirt floor is dry but the floor gets cold

Insulation will improve your temp issue more than a moistuire barrier. Is there no insulation between the joists now?

Nothing there now but I was worried about the moisture coming up and or the insulation holing the moisture could I insulate and then plastic

Please use the ANSWER THIS QUESTION box rather than the comment thing, they are trying to fix that. Does the underside of the floor and joists get damp now? Ventilate the crawl space will also drop moisture levels as will plastic on the floor. I'd cover the plastic with crushed stoe or gravel and insulation the joist bay. You can use rigid foam insulation or even sprayed in foam.